1. Field of the Invention
The present invention relates to a ground proximity warning system (GPWS) for a rotary-wing aircraft, and more particularly to an excessive altitude loss after take-off warning system for a rotary-wing aircraft which provides a warning of loss of barometric altitude after take-off as a function of the product of time and terrain clearance during take-off and go-around-after-a-missed-approach modes of flight, which minimizes nuisance warnings during certain flight maneuvers, such as ship-to-ship and oil platform-to-oil platform maneuvers by such rotary wing aircraft.
2. Description of the Prior Art
Ground proximity warning systems that warn of aircraft descent after takeoff or during a go-around after missed approach are known. Examples of such systems are disclosed in U.S. Pat. Nos. 3,946,358; 3,947,808; 3,947,810; and 4,319,218, assigned to the same assignee as the present invention. The systems disclosed in the '358 and '808 patents provide a warning if the descent rate of the aircraft exceeds a predetermined rate below a given altitude. The systems disclosed in the '810 and '218 patents generate a warning if the altitude loss after a take-off exceeds a predetermined value. While the systems mentioned above do provide a way to warn the pilot of an aircraft of a hazardous condition resulting from an excessive sink rate or from an excessive altitude loss after take-off or missed-approach phase of operation, such systems are generally designed for use in transport aircraft, and thus are not particularly suitable for use in highly maneuverable rotary-wing aircraft, such as helicopters, whose flight and operational characteristics are entirely different than those of transport aircraft. Consequently, such systems designed for transport aircraft can generate nuisance warnings during certain normal operational conditions of a rotary-wing aircraft and perhaps provide no warning or an inadequate warning during other flight conditions.
In order to resolve such problems, ground proximity warning systems for rotary-wing aircraft have been developed. Examples of ground proximity warnings systems for use in rotary wing aircraft are disclosed in U.S. Pat. Nos. 4,551,723; 4,818,992; and 4,980,684. While such systems provide adequate protection during most flight maneuvers, such systems may provide nuisance warnings during certain flight maneuvers, such as ship-to-ship and oil platform-to-oil platform maneuvers.